I’ve used three 2FA WordPress plugins so far. Here’s a review of all three of them and conclusion at the end.
1. Google Authenticator for WordPress by Julien Liabeuf
2. Google Authenticator – Two Factor Authentication by Miniorange
3. 2FAS – Two Factor Authentication by 2FAS

An unintended 301 redirect from http to https was occurring after installing a wildcard SSL certificate and turning on https in the WordPress settings > general. Took many discussions with SiteGround support to get to a reasonable conclusion.

When performing various speed tests in the previous post, Secure site / https, SSL (Speed tests on site B – Part 4), I ran into a strange problem that I couldnt solve by myself. The Time To First Byte was suddenly and consistently taking around 4 seconds, a behavior I had not seen ever before.